Pressure casting piston machines



Sept. 3, 1957 s w s 2,804,666

PRESSURE CASTING PISTON MACHINES Filed July 28. 1953 2 Sheets-Sheet lSept. 3, 1957 L. SAIVES PRESSURE CASTING PISTON MACHINES Filed July 28.1953 2 Sheets-Sheet 2 United States Patent Gfi ice PRESSURE CASTINGPISTON MACHINES Leon Saives, Billancourt, France, assignor to RegieNationale des Usines Renault, Billancourt, France, and Societe desHauts-Fourneaux et Forges dAllevard,

- Paris, France, a corporation of the French Republic Application July28, 1953, Serial No. 370,822

Claims priority, application France August 28, 1952 2 Claims. (CI.22-68) The invention has for its object various improvements applied tomachines for casting ferrous metals under pressure and particularly tothe pistons and to the ladle cylinder.

Machines adapted for casting articles under pressure are known in whichthe liquid metal, first of all poured into a ladling on ladle cylinderof special steel communicating with the mould, is displaced into themould by a hydraulic piston.

A number of disadvantages inherent in these machines are summarisedbelow:

1. The walls of the pouring hole are progressively choked and themovement of the ladle piston is thus obstructed.

2. The sealing between pistons and cylinders is obtained by wads ofsteel wool and graphite fixed on the head of the pistons. The assemblyof this packing deteriorates rapidly and ceases to. serve its purpose.

3. In certain of these machines, the passage connecting the ladlecylinder to the injection cylinder is disposed axially of the ladlecylinder. This arrangement favours the production of splashes of metalwhich solidify more quickly than the mass of the metal and these smallfragments obstruct the casting passage towards the mould.

4. The action of the injection piston on the column of liquid or viscoussteel moving towards the mould does not ensure that the compression isequally distributed 7 at all points of the mass in this column. Theresult is an imperfect filling of the mould and cavities in the finalcasting.

As regards this latter point, this unequal distribution of the pressureis explained by the factthat the moving column of metal is solidified inits external portion in contact with the cylinder and forms a solidtube, only the interior of which remains viscous. The solidifiedportions of this tube and particularly its base offer resistance to theaction of the piston and screen the viscous metal from the necessarypressure. A technique is known which consists in subjecting the viscouszone to a supplementary compressive stress by the action of a forcepiston disposed in the injection piston and cominginto action at the endof the travel of the piston. However, difliculties are presented inobtaining the sealing between the two pistons and in detaching theforcing piston from the metal after the operation.

The following arrangements obviate the aforementioned disadvantages andconstitute considerable improvements.

In the accompanying diagrammatic drawings, the figures illustrateexamples of application of the arrangements referred to and are not ofany limitative nature.

Figure 1 is a sectional view taken on line 8 of Fig. 8 showing a scraperpiston for the pouring hole.

Figure 2 shows a sealing arrangement applied to an injector piston.

Figure 3 is a sectional view of the sealing cup.

Figures 4 and 5 respectively show a sectional elevation of the end ofthe ladle cylinder and a plan view of the end of this cylinder.

Patented Sept. 3, 1957 Figures 6 and 7 respectively show by way ofexample an embodiment of a forcing piston at the commencement and end ofthe injection.

Fig. 8 is a vertical sectional view of the complete assembly of themachine in accordance with the invention.

The improvements in question are:

l.Scraper piston Figure 1 is a transverse section showing a part of apressure casting machine modified in accordance with the invention.

The wall of the pouring hole has a lining 1 of refractory material. Apiston 2 operated by a jack (not shown) may slide in the lining as faras the external level of the ladle cylinder 3. The surface and the pathof the piston are arranged in such manner that at the end of its travel,the piston may form the Wall of the ladle cylinder in order to avoid therising of the metal at the commencement of the action of the ladlepiston.

The operation of the apparatus is as follows:

Molten metal from a casting ladle is emptied into the ladle cylinder 3,the scraper piston 2 is lowered and this scrapes off the solidifiedparts adhering to the pouring hole 1. At the end of its travel, thescraper piston 2 completely closes the pouring hole 1 as indicated aboveand the ladle piston is then set in operation.

Figure 1 shows the invention applied to a pressure casting machine inwhich the ladle cylinder is horizontal. The invention is obviouslyapplicable to any machine for casting under pressure.

2.Sealing of the pistons The invention has for an object a sealingsystem applicable to pistons of all kinds and obviating thedisadvantages of the known arrangements.

The piston 4 carries a dished plate or cup 5 of the .shape shown inFigures 2 and 3.

3.Shape of the end of the ladle cylinder The shape indicated in Figures4 and 5 has for its object to obviate the aforementioned disadvantages.

The jet of metal coming from the ladle cylinder 6 is directed inaccordance with an inclined helix with an angle towards the base whichmay be of the order of 20. In order to obtain this result, thecommunication passage is constricted in the last portion A of the ladlecylinder and opens tangentially to the walls of injection cylinder 7.The liquid metal arriving tangentially is twisted helically towards thebase of the injection cylinder 7 and thus does not cause any splashes.

4.F0rcing piston The arrangement of forcing piston which has beenproposed obviates the defects which have been referred to.

Figure 6 shows by way of example one embodiment of this forcing systemwhich is applied to a casting machine in which the joint plane of themould is horizontal, the ladle cylinder i horizontal and is disposedbelow the mould, the latter being supplied at the bottom by a verticalinjection cylinder.

In Figure 6, the pistons are shown in the position at the commencementof injection.

Figure 7 shows the arrangement of the pistons on completion ofinjection.

The piston 8 is disposed in the injection cylinder 9 and has on itsinner end a cup So like cup 5 of Figs. 2 and 3.

The forcing piston is located in the forcing cylinder 11 and has on itsinner end a cup 552 like cup 5 of Figs. 2 and 3. Its diameter isapproximately two-thirds ofthe diameter of the injection cylinder andwhen at rest it leaves a free space 13 between its face and the chamber12 which communicates with the mold (not shown) through a passageway 15.

The operation of the apparatus is as follows:

After the lading cylinder piston 4 (Fig. 8) has filled the injectioncylinder 9 with liquid steel, the piston 8 is set in motion in an upwarddirection and commences to fill the chamber 12 and the mould (notshown). steel being solidified on the walls of the injection cylinder 9forms a tube. This tube offers a resistance suflicient to stopcompletely the rising movement of the injection piston before thefilling of the mould is completed. At this The moment, the metal whichhas filled the free space 13 between the chamber 12 and the forcingpiston 10 has solidified and there is then initiated the movement ofcompression of the forcing piston 10. It is the solidified metal slug13a in front of the forcing piston which directly exerts the compressivestress on the metal. Losses of metal are avoided owing to the goodadjustment of the slug in the cylinder and since the forcing piston doesnot penetrate into the viscous metal, there is no difficulty inextracting the piston. The slug 13a is removed when the cast article istrimmed.

The arrangement of the forcing piston has been given by way of exampleaxially of the injection piston.

I claim:

1. In a pressure casting piston machine in combination, means defining achamber, a passageway leading from said chamber to a mold, a forcingcylinder opening into said chamber, an injection cylinder opening intosaid chamber, a ladling cylinder communicating with said injectioncylinder, the communication between said ladling cylinder and injectioncylinder comprising a converging passageway extending from an end ofsaid ladling cylinder and opens tangentially into the injection cylinderin a downwardly inclined helical direction, a pouring passage openinglaterally from said ladling cylinder for charging a molten metal intosaid ladling cylinder, said passage having a cylindrical lining ofrefractory material, a scraping piston movable into said passage, saidpiston having a cylindrically curved inner end and being movable to aninner position in which it closes said passage and said inner end issubstantially flush with the wall of said ladling cylinder, a pistonmovable in said ladling cylinder to force metal from said ladlingcylinder helically into the injection cylinder, a piston movable in saidinjection cylinder to force molten metal into said chamber and saidforcing cylinder, said forcing cylinder being of substantially smallercross section than the injection cylinder so that molten metal forcedinto said forcing chamber solidifies to form a slug, a piston movable insaid forcing cylinder to force said slug into said chamber and therebyapply pressure to molten metal in said chamber and in said mold, and adished plate of a heat-conducting refractory metal being provided on theinner end of at least one of said pistons other than the piston in thepouring passage, said plate having cupped edges projecting away from thepiston and having the characteristic of becoming pliable at apredetermined temperature and pressure, whereby a seal is effectedbetween the piston and its corresponding cylinder when molten metal ismoved by the piston and none of the metal is permitted between thepiston and the cylinder nor to be cooled therein and bind the piston.

2. In a pressure casting piston machine in combination, an injectioncylinder, a piston reciprocable in said cylinder, a ladling cylinderdisposed at substantially right angles to said injection cylinder andcommunicating at one end with said injection cylinder, said end of theladling cylinder converging progressively to provide a connectingpassageway of reduced cross section that opens tangentially into theinjection cylinder in a downwardly inclined helical direction, means forcharging a molten metal into said ladling cylinder and a piston movablein said ladling cylinder to force molten metal through said convergingpassageway helically into said injection cylinder.

References Cited in the file of this patent UNITED STATES PATENTS969,539 Kitchen Sept. 6, 1910 1,935,059 Pack Nov. 14, 1933 1,941,199Brotz Dec. 26, 1933 2,112,342. Lester Mar. 29, 1938 2,181,157 Smith Nov.28, 1939 2,183,112 Vontobel Dec. 12, 1939 2,206,211 Wagner July 2, 19402,564,885 De Sternberg Aug. 21, 1951 FOREIGN PATENTS 336,129 GreatBritain Oct. 9, 1930 376,319 Great Britain July 4, 1932

